Field Explanations

Batch Size - The number of gallons you plan to put into the primary fermenter.

Grain Bill - Pounds of barley malt, rye, or wheat used in the recipe - excludes sugars, honey, etc. that do not absorb water readily.

Boil Time - Number of hours to boil the wort (e.g., a 90 minute boil would be 1.5 hrs)

Trub Loss - The trub, cold-break, hops, chiller loss, and excess wort left when transfering from the boil kettle.

Equipment Loss - The amount wort left at the bottom of the mash tun after emptying it.

Mash Thickness - In quarts/lb., the ratio of sparge water to grain to be used in the mash. An average value to use is 1.33 qts/lb.

Grain Temperature - The measured temperature of the crushed grains at the time of dough-in.

Target Mash Temperature - The temperature at which you plan to hold your mash in the mash tun.

Wort Shrinkage - The percentage which the volume of boiling wort shrinks when cooling to 68 degrees. This is a well-accepted constant value of 4%.

Grain Absorption Constant - This is the number of gallons of water absorbed per pound of grain during the mash in your system. You will
need to measure and adjust this value for your system parameters as they can vary greatly. Ray Daniels in Designing Great Beers recommends a value of 0.20 and
Denny Conn observes a value of 0.10 in his system. Default is set at the value for my system.

Perecent Boiloff per Hour - The percentage of wort boiled off into the atmosphere per hour during boil. Again, for best results, you will need to observe this value in your system
and change as the strength of your burner, dimensions of your boil pot, etc. can come into play. This can be calculated noting the preBoil and postBoil volumes at
the one-hour mark when boiling your next wort and plugging it into the formula : Evaporation Pct. = 100 - (postBoil volume * 100 / preBoil volume)

Total Water Needed - The total gallons of Mash & Sparge water needed for this brewing session.

Mash Water Needed - Gallons of water needed for the mash based on your Mash Thickness value and Grain Bill size.

Sparge Water Needed - Water left for sparging after the mash water has been subtracted from the total water needed.

Strike Temperature - Temperature at which to dough-in your mash. This value assumes that your mash tun has been pre-heated.

Pre-Boil Wort Produced - Total Wort produced by mashing + sparging. This can be useful to figure out if your wort fits into your boil kettle. (Thanks for the suggestion Art.)

More Information and how these values are calculated can be found HERE